How do you personally use energy?

How much is our increased use of energy to blame for global warming?

• A portion of the energy we use comes originates from the sun, the most obvious examples being solar energy and wind energy. But, a larger portion of our energy is obtained not from the sun and via other methods, for example via gasoline, coal, nuclear, or geothermal. All of the energy from these sources eventually gets converted to heat in one way or another  -- for example, gasoline in a car (the energy is either turned to heat via the brakes, or lost due to inefficiencies in the engine, wheels, etc.). All of this excess heat that's created from sources other than the sun dissipates in the air, which artificially heats up the earth. But how much do these extra heat sources contribute to global warming?

• Answer:

  On a global basis: Insignificant. A very rough estimate on the cumulative temperature rise directly attributable to human energy consumption is of the order of magnitude 0.01C (0.02F). The temperature rise due to associated human-caused emissions of greenhouse gases so far is about 100 times larger than that. Local effects can of course be much larger (or for that matter smaller), but I will only deal with the global scale, and global averages. Wikipedia: The estimates of remaining non-renewable worldwide energy resources  vary, with the remaining fossil fuels totaling an estimated 0.4 YJ (1 YJ  = 10^24J) and the available nuclear fuel such as uranium exceeding 2.5 YJ. Fossil fuels range from 0.6 to 3 YJ if estimates of reserves of methane clathrates are accurate and become technically extractable. The total energy flux  from the sun is 3.8 YJ/yr, dwarfing all non-renewable resources.[1] That is, in merely two years the sun provides more energy than we have estimated to have available in the form of: Coal Natural gas Tar sands and other non-traditional (and possibly ultimately partially inaccessible) sources of carbon based compounds Uranium etc., etc. for the rest of the course of human history. Put it in other words: the total solar influx on the atmosphere is about 1.4kW/m². Multiply this with the cross section of the Earth, and we get about 1.78*10^17W. How much energy do we use at the moment, then? According to [2], we consumed in 2010 some 500EJ during that year, making for an average of 1.6*10^13 W, out of which 11.3% (same source) were biomass, and had thus once reduced the impact of the heating of the sun. But: let's disregard that, thereby overstating the effect of our energy consumption. Then, the sun provides us with roughly 10 000 times as much energy as humanity consumes. Not quite all of this will actually heat the atmosphere, as some will be reflected and return out into space as light: assuming a conservative albedo (=percentage of light energy that's reflected back into space) of 40% (I'm pretty sure it's smaller than this, meaning even more of sun's energy would be absorbed), it still means that 60% is absorbed by atmosphere, ground, or water. That is, the sun heats the world some 6000 times more than humanity does. *** Begin math-y stuff *** (included mostly for the heck of it) Now, this is after all talk about energy. Can we give a ballpark estimate on how this translates into temperature differences? Yes, but note that this is a very rough estimate! I wouldn't trust this to more than an order of magnitude. Assume that Earth is basically a black-body, that Sun contributes with power [math]P = a T^4[/math] (where [math]a[/math] is a constant that amongst other things depend on the radius of the Earth and its albedo, and T is temperature of the Earth in Kelvin (roughly 290K)). Assume further that humanity contributes with an extra amount [math]\Delta P = \frac{P}{6000}[/math], contributing to a small rise in temperature [math]\Delta T[/math], meaning that [math]P+\Delta P = a(T+\Delta T)^4[/math], or [math]1+\frac{\Delta P}{P} = (1+\frac{\Delta T}{T})^4[/math]. Solving for [math]\Delta T[/math] gives that the direct heating contribution by our use of energy is on the order of 0.01K, corresponding to about 0.02F; effects from greenhouse gases and other second-order effects, as well as feed-backs, not included, so don't take this for anything else than what it is: a ballpark estimate of one very narrow (and apparently quite small) contribution to global climate change. *** End math-y stuff *** Also note that the "math-y" calculation does not take into account the time span needed to achieve this temperature rise. It is simply an estimate on the cumulative temperature increase achievable - given a constant total human energy output of  500EJ/year and no GHG effects - before thermodynamics assert that a new equilibrium has been achieved. To estimate how far temperature could  rise in a given year due direct effects from human energy use, we would  need to estimate the thermal mass of the outer layers of the Earth, as in, those layer taht we can directly heat up (we won't influence the temperature of the core anytime soon). But that would in the end only provide us with a time scale, not a limit on how far the temperature would go. And then I haven't even started on the amount of heating that is provided by heat transfer from Earth's mantle, or from radioactive decay in the crust. I don't know how to estimate these contributions, but they would certainly contribute in the direction of making humanity's contribution to direct heating of the Earth even less significant. Also compare where some more official estimates of the anthropogenic heat flux (AHF) is given. [1] World energy consumption. (2012, May 24).  In Wikipedia, The Free Encyclopedia. Retrieved 06:02, May 27, 2012, from http://en.wikipedia.org/w/index.php?title=World_energy_consumption&oldid=494219526 [2] World energy consumption - beyond 500 exajoules. (2012, Feb 16). Retrieved 06:18, May 27, 2012, from http://www.energybulletin.net/stories/2012-02-16/world-energy-consumption-beyond-500-exajoules